1. Journal Basic Science And Technology, 1(2),5-9,2012
ISSN : 2089-8185
The Effect of Water Content Hydrogen Peroxide to
The Structure of HTPB (Hydroxy Terminated
Polybutadiene) Product as Radically Polymerization
of Butadiene
A Heri Budi Wibowo
Pusat Teknologi Roket
LAPAN
Bogor, Indonesia
heribw@gmail.com d
Polymerization of butadiene can be proccess by free
radical and ionic polymerization. The advantages of ionic
polymerization is can produce HTPB with narrow molecule
weight distribution and dominan cis-1,4 structure, but cost of
production is expensive [2]. The special treatment must be
applied to maintain vacuum process. The free radical
polymerization is simple process and many cheap catalyst,
but product HTPB is broad molecular weight distribution . For
industry application, the free radical polymerization is the
effective process because ease for process and cheap. HTPB
can be made with catalyst hydrogen peroxide in alcohol
solvent. The solvents are etanol, butanol, propanol, etc [8,9].
Abstract—HTPB is resin that used as the best fuel binder
propellant. HTPB is strategic, expensive, and renewable. For this
application, HTPB can be synthesis by radically polymerization
of butadiene. One of catalyst than ussually can be used is
hydrogen peroxide. The problem of the use of this catalyst is
water content that can inhibit the polymerization process. This
paper discuss the effect of water content of hydrogen peroxide on
structur of HTPB base on polymerization of butadiene. The raw
materials used were fresh butadiene 98%. The reactor used was
a three neck flask 500 mL equipped with a thermocouple, a
stirrer, a sample syringe, and a hot or cold water circulator.
Catalyst is hydrogen peroxide with water content 30 – 50%. The
reaction is conducted for 70 minutes at 180oC and 350 psig. The
HTPB product is analyzed by FTIR spectrometer. The decreased
of water content of hydrogen peroxide is increase efectivity of
catalyst on polymerization. The cis-1,4 HTPB is increase and the
vynil 1,2-structure of HTPB is decrease.
One of the problem on butadiene polymerization is the
water content of hydrogen peroxide. Butadiene is not soluble
in water. Action of catalyst hydrogen peroxide is free radical
hydroxyl forming by decomposition. The excess of water is
inhibit the radical hydroxyl forming so decreased the
effectivity of this catalyst. The excess of water may be affect
on structure of HTPB by hydroxyl bonding on polymer growth
[11].
Keywords- HTPB, polybutadiene, radical polymerization
I.
INTRODUCTION
TThe investigation of HTPB as propellant fuel binder is
very important in aerospace technology authority framework.
The solid propellant is consists of ammonium perchlorate as
oxydator, binder, and material additive. The most used of
propellant binder is polyurethane based on HTPB (Hidroxy
Terminated Polybutadiene). HTPB is an expensive, strategic,
and unrenewable. HTPB is polymer base on butadiene
monomer with the end functional groups is hydroxyl (OH)
[3].
The aim of this investigation is to discover the efectivity of
catalyst hydrogen peroxide on HTPB forming and their
structures. Based on this parameters, we will to find out
polymerization proccess condition are able to fullfill the term
of suitable solid propellant binder.
II.
THEORY
A. Structure of Polybutadiene
The main characterization of polymer HTPB are molecular
weight distribution and structure (configuration). The
fexibility or hardness of polyurethane base on HTPB is
affected by the molecular weight distribution and structure of
HTPB. Increased of molecular weight distribution of HTPB
can produce harder polyurethane. The increase of cis-1,4
structure of HTPB is contributed on flexibility of
polyurethane, but the increase of trans-1,4 structure of HTPB
is contributed on hardness of polyurethane [7].
Polybutadiene is
a polymer or a series of butadiene monomer compounds.
Butadiene is
a
compound that has
the possibility
to crosslinking reaction with other compounds at all owned
by the
C atom, the atom C coding as
in
figure
1. Butadiene polymerization
reaction occurs with covalent bonding occurs between the CHCH group with others through adisi1 reaction [4,7].
5

2. Journal Basic Science And Technology, 1(2),5-9,2012
ISSN : 2089-8185
polymerization in
which initiation occurs via a free
radical. Operating conditions include a reaction and the
reaction media system operating conditions (temperature, press
ure, inert,and reagent composition)
[3]. Based
on the polymerization reaction
medium can
occur with a
bulk, solution, suspension, and emulsion
systems. Polymer structures that occur can be predicted based
on the
reaction
mechanism that
occurs so
it
can
be identified factors that
influence the
structure
of
the polybutadiene [3,5].
n (CH2-CH=CH-CH2 )
(CH2=CH-CH=CH2)n (1)
Bond addition reactions can occur in two ways. The first
way is the reaction between the C atom by C no 1 to C no
4 of the
other compounds
to
form
a
bond
butadiene adduct 1.4. Addition of 1.4 will lead to bond the two
structures based on geometric shapes. If the group H at the
position opposing the so-called bond in
trans position. If
the group H on the
position side
by
side each
other so called cis-bond at position 5 [4,8].
B. Radical Polymerization of Butadiene
Free radical polymerization occurs through the formation
of free radical. Free radicals can be generated from the
redox reactions or reactions of
radicalization. Redox reactions like the
reaction of
iron (III) sulfate with manganese
oxide to
form iron (II) sulfate and hydroxyl radicals (OH.) or pyrolysis
of hydrogen peroxide to produce free radicals. Free
radical then
reacts with
butadiene to
form radicals (CH2CH2CH2CH2OH. or MOH.). Propagation
reaction initiated by reaction with butadiene radical other to
form a
dimer radical. The
polymer
is
growth. Radical reaction with butadiene will stop in several
ways, namely the inter-radical termination, radical with the
growing polymer, or in the presence of other compounds [9,
10]. Reaction mechanism can be shown on this equation.
H2O2
2 HO.
(4)
2 HO.
(5)
H2O2
(2)
The second way occurs through the bond between
the C atom No. 1 with butadiene number 2 on the other, the
bond will be formed at a position 1.2 or called bonds at
the vinyl position (equation 3).
M + MOH.
M + M2OH.
M + MxOH.
(3)
M2OH.
M3OH.
Mx+1OH.
(6)
(7)
(8)
Polymer growth occurs through a random system, where
the growth of radical reactions do not occur one on one, but
occur simultaneously, and the reaction of butadiene with not
only the polymer radicals are formed, but also the reaction
between the growing polymer with another polymer that is
growing. Known free radical polymerization reaction is very
fast, so the reaction between polymer radicals occurs at
random. Therefore, the radical polymerization will produce a
polymer with a molecular weight distribution is not uniform.
Polymer growth can be stopped by radical chain reactions
bimolekuler pair through the coupling reaction or a
combination (equation 9) and the disproportionate reaction by
hydrogen atom transfer (equation 10). If equation 7 is the case,
then the polymer is a polymer formed by a single hydroxyl end
groups.
MxOH. + MyOH.
HOMxMyOH
(9)
MxOH. + MyOH.
HOMx + MyOH
(10)
Configuration can
be
either cis, trans, and vynil. The
existence of two double bonds in the polymerization
process can give adduct 1.4- which can
be
either cis-1,4
and trans-1,4. The
existence
of a
single
bond to
generate vinyl structure or 1.2 with the
possibility
of isotactic structure,
sindiotaktik, and static. Structure
of polybutadiene with cis-1, 4 - the higher
is
soft, good dynamic properties, low hysteresis and
good abrasion, the glass transition temperature up to 102oC.
Polybutadiene with the
dominant structure
of trans1,4 is a resilient elastomer,
hard,
glass
transition temperature 107oC to 83oC. Polybutadiene with isotactic structure
of
the dominant 1.2 -sindiotaktic is
a brittle, crystalline material that has a low solubility.
Polybutadiene structure that occurs will depend on the
operating conditions
of
the
reaction and
the mechanism through which the reaction. There are two
mechanisms
of polybutadiene reaction, the ionic polymerization in
which initiation occurs through cation and anion, and radical
Reaction
rate equation is
expressed by the
reduced monomer per unit
time,
is
a
function of
the monomer and the radical chain. Every time the value of the
radical concentration is
proportional
to
the initial initiator concentration.
6

3. Journal Basic Science And Technology, 1(2),5-9,2012
ISSN : 2089-8185
-d[M]/dt = kp[M.][M]
(11)
vynil configuration at wavelength 710 cm-1, 970 cm-1, and 910
cm-1.
Effect of the reaction temperature
follow the
type operation follow Arhenius equation [4,7]. Effect of
catalyst efectivity (water content) is decrease the activation
energy. So effect of temperature (T) and water content of
hydrogen peroxide (w) to reaction rate constant of cis
polymerization (kpc), trans polymerization (kpt), and vynil
polymerization (kpv) are expressed like eq. 12, 13, and 14. The
symbol of Ec, Ac, and R are represented of activation energy,
collision frequency factor, and ideal gas constant.
(12)
(13)
(14)
Fig 1. Spectra of HTPB.
III.
METODOLOGY AND RESULTS
The kinetic of polymerization is identified by decrease of
pressure of reactor as representated of monomer concentration
(M). Initial pressure is 350 psig, and at the end of reaction,
pressure is 14,7 psig. The decrease of reactor pressure every
time is shown at fig 2. Trend of the line is exponential so the
reaction is first order follow the equation (11). The value of
total reaction rate constant (kpc+kpt+kpv) is the slope of curve
ln [M] vs t.
A. Material
The raw materials used were fresh distilled butadiene 98%.
The solvent is ethanol 96,5% withaout pretreatment. The
catalyst is solution hydrogen peroxide 30 %, 32 %, 35 %, and
50%.
B. Experiment
The reactor used was a three neck flask 500 mL equipped
with a thermocouple, a stirrer, a sample syringe, and a hot or
cold water circulator. The reaction is conducted for 70 minutes
at 180oC and 350 psig. The HTPB structure is analyzed by
FTIR spectrometer. Cis 1,4-, trans 1,4- and vynil structure are
shown by absorbtion at wave length 710 cm-1, 970 cm-1, and
910 cm-1. To study the kinetic of polymerization, data record is
decrease of butadiene pressure as function of time.
C. Discuss
To prove the statement, the trial has been carried
out by radical polymerization of butadiene using hydrogen
peroxide initiator
with
ethanol
as
solvent. With
the operating conditions
of 170-210oC reaction temperature
and initial pressure 350 psi, HTPB product is identified by
FTIR spectra shown in figure 1. The product is wash by
aquadest and benzen, then dried with vacuum oven at 60oC
over 1 hour, and analyzed. The HTPB is represented by
absorbstion at 1735cm-1 and spesific structure of cis, trans, and
Fig 2. Decreasing of pressure as function of time
For study of kinetic of polymerization include cis, tans,
and vynil structure formation, the increase of each structure
form is identified by area of absorbtion at wavelength 710 cm1
, 970 cm-1, and 910 cm-1. The area of spectra at wavelength
7

4. Journal Basic Science And Technology, 1(2),5-9,2012
ISSN : 2089-8185
710 cm-1, 970 cm-1, and 910 cm-1 follow the table 1 as
dominant. The cis structure can be optimized by change the
represented of persen composition polymer HTPB. The
reaction temperature.
kinetic of formation of cis, trans, and vynil structure is
Effect of temperature on reaction rate constant is measure
expressed by eq. 15, 16, and 17.
by extrapolation of ln k vs 1/T so the Arhenius constant A and
-d[M]c/dt = (kpc) [M]
(15)
-d[M]t/dt = (kpc) [M]
(16)
-d[M]v/dt = (kpc) [M]
E can be find by their slope. To study effect water content of
hydrogen peroxide to reaction rate constant, curve reaction
rate constant versus water content is power type extrapolation.
By trendline analysis, the power index can be predicted (figure
4).
(17)
TABLE I.
Time
(min)
COMPOSITION OF STRUCTURE HTPB AS
FUNCTION TIME
Area spectra FTIR at point wave length
710 cm-1
910 cm-1
970cm-1
0
100
135
360
10
120
150
379
20
130
165
398
30
140
175
417
40
150
190
423
50
160
196
437
60
165
198
440
70
167
200
445
Figure 4. graph ln k vs (1/T)
To measure the reaction rate constans of kpc, kpt, and kpv, then
data concentration of polymer with cis, trans, and vynil
structure every time is extrapolation in graph ln [M]c,t,v vs t.
By trend analysis, the slope of graph ln [M]c,t,v vs t is kpc, kpt,
and kpv. The increase of structure of cis, trans, and vynil
formation is proporsional with concentration of cis, trans, and
vynil.
Fig 5. Effect water content to reaction rate constant
Generally, increase water content is decrease
the
efectivity of catalyst, so reaction rate of polymerization is
increase. In experiment, if water content of hydrogen peroxide
is less than 30%, HTPB product is no formed because the
hydroxyl radical is not produced. The effect of temperature
and water content are combined in expression 18, 19, and 20.
Figure 3. graph [M] vs t
Based on figure 3, the rate of vynil structur formation is
greater than cis or trans formation. It’s clearly that radical
polymerization have tendency to form vynil structure
(18)
8

5. Journal Basic Science And Technology, 1(2),5-9,2012
ISSN : 2089-8185
(19)
REFERENCES
(20)
[1]
[2]
Based on index power of w on equation 18, 19, 20
expressed that reaction rate of cis, trans, and vynil structure
formation is affected by water content of hydrogen peroxide.
The effect of water content on cis formaton less fast than trans
and vynil formation. The effect of temperature to reaction rate
is follow the Arhenius equation. The increase of temperature is
contribute effect follow trans structure formation > vynil
formation > cis structure formation.
[3]
[4]
[5]
IV.
CONCLUSION
[6]
Generally, increase water content is decrease the efectivity
of catalyst, so reaction rate of polymerization is increase. In
experiment, if water content of hydrogen peroxide is less than
30%, HTPB product is no formed because the hydroxyl radical
is not produced. Reaction rate of cis, trans, and vynil structure
formation is affected by water content of hydrogen peroxide.
The effect of water content on cis formaton less fast than trans
and vynil formation. The effect of temperature to reaction rate
is follow the Arhenius equation. The increase of temperature is
contribute effect follow trans structure formation > vynil
formation > cis structure formation.
[7]
[8]
[9]
[10]
[11]
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